Actividad repelente e insecticida de cuatro aceites esenciales de plantas recolectadas en Chocó-Colombia contra Tribolium castaneum / Repellent and insecticidal activity of four essential oils from plants recolleted in Chocó-Colombia against Tribolium castaneum

This study aimed to determine the repellent and insecticidal activity of four essential oils (EOs) from plants collected in the Chocó rain forest, Colombia, against T. castaneum . Conventional hydrodistillation was used to obtain the EOs. The repellent and insecticidal activities were evaluated by the preference area and gas dispersion methods, espectively. Statistical differences (p<0.05) were determined by applying a student's t-test. EOs of Siparuna guianensis, S. conica, Piper marginatum, and Nectandra acutifolia showed excellent repellent properties as the main findings, highlighting S. conicaEO with 84% repellency (1-hµL/cm2), while P. marginatum showed to be bioactive to the dose of 500 µL/mL (72 h), inducing mortality of 100% of the exposed population. In conclusion, the results evidenced the repellent properties of the EOs evaluated against T. castaneum , which allows us to conclude that these plant species are potential natural sources producing bio-repellents that contribute to the integrated control of T. castaneum.

Se evaluaron cuatro aceites esenciales (AEs) de plantas recolectadas en la selva pluvial del Chocó, Colombia, para determinar su actividad repelente e insecticida contra T. castaneum. Los AEs fueron obtenidos por hidrodestilación convencional. Las actividades repelentes e insecticidas se evaluaron por los métodos de área de preferencia y dispersión de gas, respectivamente. Las diferencias significativas (p<0,05) fueron determinadas aplicando una prueba t de student. Los AEs de Siparuna guianensis, S. conica, Piper marginatum y Nectandra acutifolia mostraron excelentes propiedades repelentes, destacando el AE de S. conicacon un 84% de repelencia (1µL/cm2), mientras que el AE de P. marginatummostró ser bioactivo a la dosis de 500 µL/mL (72 h) al inducir la mortalidad del 100% de la población expuesta. Se concluye que estas especies de plantas son fuentes naturales potencialmente viables para la producción de biorepelentes que contribuyan en el control integrado de T. castaneum.

Laboratory evaluation of the contact irritancy of a clothianidin solo formulation vs. clothianidin-deltamethrin mixture formulations for indoor residual spraying against pyrethroid-resistant Anopheles gambiae sensu lato.

BACKGROUND: Clothianidin-based indoor residual spraying (IRS) formulations have become available for malaria control as either solo formulations of clothianidin or a mixture of clothianidin with the pyrethroid deltamethrin. While both formulations have been successfully used for malaria control, studies investigating the effect of the pyrethroid in IRS mixtures may help improve our understanding for development of future IRS products. It has been speculated that the irritant effect of the pyrethroid in the mixture formulation may result in shorter mosquito contact times with the treated walls potentially leading to a lower impact. METHODS: We compared contact irritancy expressed as the number of mosquito take-offs from cement surfaces treated with an IRS formulation containing clothianidin alone (SumiShield® 50WG) to clothianidin-deltamethrin mixture IRS formulations against pyrethroid-resistant Anopheles gambiae sensu lato under controlled laboratory conditions using a modified version of the World Health Organisation cone bioassay. To control for the pyrethroid, comparison was made with a deltamethrin-only formulation. Both commercial and generic non-commercial mixture formulations of clothianidin and deltamethrin were tested. RESULTS: The clothianidin solo formulation did not show significant contact irritancy relative to the untreated control (3.5 take-offs vs. 3.1 take-offs, p = 0.614) while all deltamethrin-containing IRS induced significant irritant effects. The number of take-offs compared to the clothianidin solo formulation (3.5) was significantly higher with the commercial clothianidin-deltamethrin mixture (6.1, p = 0.001), generic clothianidin-deltamethrin mixture (7.0, p < 0.001), and deltamethrin-only (8.2, p < 0.001) formulations. The commercial clothianidin-deltamethrin mixture induced similar contact irritancy as the generic clothianidin-deltamethrin mixture (6.1 take-offs vs. 7.0 take-offs, p = 0.263) and deltamethrin-only IRS (6.1 take-offs vs. 8.2, p = 0.071), showing that the irritant effect in the mixture was attributable to its deltamethrin component. CONCLUSIONS: This study provides evidence that the enhanced contact irritancy of the pyrethroid in clothianidin-deltamethrin IRS mixtures can shorten mosquito contact times with treated walls compared to the clothianidin solo formulation. Further trials are needed to directly compare the efficacy of these formulation types under field conditions and establish the impact of this enhanced contact irritancy on the performance of IRS mixture formulations containing pyrethroids.

Did the prolonged residual efficacy of clothianidin products lead to a greater reduction in vector populations and subsequent malaria transmission compared to the shorter residual efficacy of pirimiphos-methyl?

BACKGROUND: The residual activity of a clothianidin + deltamethrin mixture and clothianidin alone in IRS covered more than the period of malaria transmission in northern Benin. The aim of this study was to show whether the prolonged residual efficacy of clothianidin-based products resulted in a greater reduction in vector populations and subsequent malaria transmission compared with the shorter residual efficacy of pirimiphos-methyl. METHODS: Human bait mosquito collections by local volunteers and pyrethrum spray collections were used in 6 communes under IRS monitoring and evaluation from 2019 to 2021. ELISA/CSP and species PCR tests were performed on Anopheles gambiae sensu lato (s.l.) to determine the infectivity rate and subspecies by commune and year. The decrease in biting rate, entomological inoculation rate, incidence, inhibition of blood feeding, resting density of An. gambiae s.l. were studied and compared between insecticides per commune. RESULTS: The An. gambiae complex was the major vector throughout the study area, acounting for 98.71% (19,660/19,917) of all Anopheles mosquitoes collected. Anopheles gambiae s.l. collected was lower inside treated houses (45.19%: 4,630/10,245) than outside (54.73%: 5,607/10,245) after IRS (p < 0.001). A significant decrease (p < 0.001) in the biting rate was observed after IRS in all departments except Donga in 2021 after IRS with clothianidin 50 WG. The impact of insecticides on EIR reduction was most noticeable with pirimiphos-methyl 300 CS, followed by the clothianidin + deltamethrin mixture and finally clothianidin 50 WG. A reduction in new cases of malaria was observed in 2020, the year of mass distribution of LLINs and IRS, as well as individual and collective protection measures linked to COVID-19. Anopheles gambiae s.l. blood-feeding rates and parous were high and similar for all insecticides in treated houses. CONCLUSION: To achieve the goal of zero malaria, the optimal choice of vector control tools plays an important role. Compared with pirimiphos-methyl, clothianidin-based insecticides induced a lower reductions in entomological indicators of malaria transmission.

Mutations and intron polymorphisms in voltage-gated sodium channel genes of different geographic populations of Culex pipiens pallens/Culex pipiens quinquefasciatus in China.

BACKGROUND: Culex pipiens pallens and Culex pipiens quinquefasciatus are the dominant species of Culex mosquitoes in China and important disease vectors. Long-term use of insecticides can cause mutations in the voltage-gated sodium channel (vgsc) gene of mosquitoes, but little is known about the current status and evolutionary origins of vgsc gene in different geographic populations. Therefore, this study aimed to determine the current status of vgsc genes in Cx. p. pallens and Cx. p. quinquefasciatus in China and to investigate the evolutionary inheritance of neighboring downstream introns of the vgsc gene to determine the impact of insecticides on long-term evolution. METHODS: Sampling was conducted from July to September 2021 in representative habitats of 22 provincial-level administrative divisions in China. Genomic DNA was extracted from 1308 mosquitoes, the IIS6 fragment of the vgsc gene on the nerve cell membrane was amplified using polymerase chain reaction, and the sequence was used to evaluate allele frequency and knockdown resistance (kdr) frequency. MEGA 11 was used to construct neighbor-joining (NJ) tree. PopART was used to build a TCS network. RESULTS: There were 6 alleles and 6 genotypes at the L1014 locus, which included the wild-type alleles TTA/L and CTA/L and the mutant alleles TTT/F, TTC/F, TCT/S and TCA/S. The geographic populations with a kdr frequency less than 20.00% were mainly concentrated in the regions north of 38° N, and the geographic populations with a kdr frequency greater than 80.00% were concentrated in the regions south of 30° N. kdr frequency increased with decreasing latitude. And within the same latitude, the frequency of kdr in large cities is relatively high. Mutations were correlated with the number of introns. The mutant allele TCA/S has only one intron, the mutant allele TTT/F has three introns, and the wild-type allele TTA/L has 17 introns. CONCLUSIONS: Cx. p. pallens and Cx. p. quinquefasciatus have developed resistance to insecticides in most regions of China. The neighboring downstream introns of the vgsc gene gradually decreased to one intron with the mutation of the vgsc gene. Mutations may originate from multiple mutation events rather than from a single origin, and populations lacking mutations may be genetically isolated.

Physical durability and insecticidal activity of long-lasting insecticidal nets in Cruzeiro do Sul, Brazil.

Vector control is one of the principal strategies used for reducing malaria transmission. Long-lasting insecticidal bed nets (LLINs) are a key tool used to protect populations at risk of malaria, since they provide both physical and chemical barriers to prevent human-vector contact. This study aimed to assess the physical durability and insecticidal efficacy of LLINs distributed in Cruzeiro do Sul (CZS), Brazil, after 4 years of use. A total of 3000 LLINs (PermaNet 2.0) were distributed in high malaria risk areas of CZS in 2007. After 4 years of use, 27 'rectangular' LLINs and 28 'conical' LLINs were randomly selected for analysis. The evaluation of physical integrity was based on counting the number of holes and measuring their size and location on the nets. Insecticidal efficacy was evaluated by cone bioassays, and the amount of residual insecticide remaining on the surface of the LLINs was estimated using a colorimetric method. After 4 years of use, physical damage was highly prevalent on the rectangular LLINs, with a total of 473 holes detected across the 27 nets. The upper portion of the side panels sustained the greatest damage in rectangular LLINs. The overall mosquito mortality by cone bioassay was < 80% in 25/27 rectangular LLINs, with panel A (at the end of the rectangular bednet) presenting the highest mortality (54%). The overall mean insecticide concentration was 0.5 µg/sample, with the bednet roof containing the highest average concentration (0.61 µg/sample). On the conical LLINs, 547 holes were detected, with the bottom areas sustaining the greatest damage. The cone bioassay mortality was < 80% in 26/28 of the conical LLINs. The mean insecticide concentration was 0.3 µg/sample. After 4 years of use, the insecticidal efficacy of the LLINs was diminished to below acceptable thresholds.

Comparative biotoxicity study for identifying better alternative insecticide especially green nano-emulsion which used as mosquitocides.

This research work was planned to test biosafety of different nanomaterials on the different animals models. These nanoparticles were previously used as potential insecticides of mosquito larvae. The biosafety of these nanoproducts were evaluated on certain organs of non target animals that associated with mosquito breeding sites in Egypt. Animal organs such as the kidneys of rats, toads, and the fish's spleen were used as models to study the biological toxicity of these nanomaterials. After 30 days of the animals receiving the nanomaterials in their water supply, different cell mediated immune cells were assessed in these tissues. Both TNF-α and BAX immuno-expression were also used as immunohistochemical markers. Histopathology was conducted to detect the effect of the tested nanoproducts at the tissue level of the liver and kidneys of both the rats and toads. Green nanoemulsion of the lavender essential oil was relatively more effective, safe, and biodegradable to be used as insecticides against mosquito larvae than the metal-based nanomaterials.

Design, synthesis, and evaluation of novel arecoline-linked amino acid derivatives for insecticidal and antifungal activities.

A series of arecoline derivatives with amino acid moieties were designed and synthesised using an acylamide condensation strategy, taking arecoline as the foundational structure. The insecticidal efficacy of these compounds against Aphis craccivora and Tetranychus cinnabarinus was evaluated. Notably, derivatives 3h and 3i demonstrated superior insecticidal activity compared with arecoline. Additionally, 3h and 3i showed good fungicidal effectiveness against two types of plant fungi. Moreover, molecular docking analyses suggested that 3h and 3i could affect the nervous systems of A. craccivora and T. cinnabarinus by binding to neuronal nicotinic acetylcholine receptors. These findings suggest that compounds 3h and 3i represent promising leads for further development in insecticide and fungicide research.

Reassessing clinical presentations of emamectin benzoate poisoning: A comprehensive study.

BACKGROUND: The mechanism of emamectin benzoate (EMB-a macrocyclic lactone insecticide like abamectin) action involves the disruption of glutamate-gated chloride channels and GABA receptors in insects, leading to paralysis and death. EMB overdose can breach the blood-brain barrier, resulting in severe poisoning and altered consciousness. AIM: Review EMB poisoning presentations in patients and reevaluate clinical manifestations. MATERIALS AND METHODS: This retrospective study reviewed (August 31, 2008-August 31, 2023) medical university hospital records. We analyzed symptoms, patient characteristics, vital signs, Glasgow Coma Scale scores, laboratory findings, and outcomes. RESULTS: Ten patients (males: 6, females: 4, median age = 64.5 years) experienced EMB poisoning. Common symptoms included sore throat, gastrointestinal distress, dyspnea, and altered consciousness; two patients showed laryngeal corrosive injuries. Management involved activated charcoal administration, gastric lavage, and intensive care unit admission. DISCUSSION: Sore throat and corrosive injuries were distinctive presentations of EMB poisoning, warranting vigilance. Potential mechanisms of corrosive injury include skin and eye irritation effects of EMB, the solvents of which might exert corrosive action. CONCLUSION: EMB poisoning manifests as diverse symptoms, including sore throat, gastrointestinal symptoms, central nervous system depression, and potential aspiration pneumonia. Recognizing and promptly managing EMB poisoning are crucial for enhancing patient outcomes and minimizing complications.

Cereal leaf beetle-associated bacteria enhance the survival of their host upon insecticide treatments and respond differently to insecticides with different modes of action.

The cereal leaf beetle (CLB, Oulema melanopus) is one of the major cereal pests. The effect of insecticides belonging to different chemical classes, with different mechanisms of action and the active substances' concentrations on the CLB bacterial microbiome, was investigated. Targeted metagenomic analysis of the V3-V4 regions of the 16S ribosomal gene was used to determine the composition of the CLB bacterial microbiome. Each of the insecticides caused a decrease in the abundance of bacteria of the genus Pantoea, and an increase in the abundance of bacteria of the genus Stenotrophomonas, Acinetobacter, compared to untreated insects. After cypermethrin application, a decrease in the relative abundance of bacteria of the genus Pseudomonas was noted. The dominant bacterial genera in cypermethrin-treated larvae were Lactococcus, Pantoea, while in insects exposed to chlorpyrifos or flonicamid it was Pseudomonas. Insecticide-treated larvae were characterized, on average, by higher biodiversity and richness of bacterial genera, compared to untreated insects. The depletion of CLB-associated bacteria resulted in a decrease in larval survival, especially after cypermethrin and chlorpyrifos treatments. The use of a metagenome-based functional prediction approach revealed a higher predicted function of bacterial acetyl-CoA C-acetyltransferase in flonicamid and chlorpyrifos-treated larvae and tRNA dimethyltransferase in cypermethrin-treated insects than in untreated insects.

Toxicity of Cry- and Vip3Aa-Class Proteins and Their Interactions against Spodoptera frugiperda (Lepidoptera: Noctuidae).

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is one of the most important insect pests affecting corn crops worldwide. Although planting transgenic corn expressing Bacillus thuringiensis (Bt) toxins has been approved as being effective against FAW, its populations' resistance to Bt crops has emerged in different locations around the world. Therefore, it is important to understand the interaction between different Bt proteins, thereby delaying the development of resistance. In this study, we performed diet-overlay bioassays to evaluate the toxicity of Cry1Ab, Cry1Ac, Cry1B, Cry1Ca, Cry1F, Cry2Aa, Cry2Ab, Vip3Aa11, Vip3Aa19, and Vip3Aa20, as well as the interaction between Cry1Ab-, Cry1F-, Cry2Ab-, and Vip3Aa-class proteins against FAW. According to our results, the LC50 values of Bt proteins varied from 12.62 ng/cm2 to >9000 ng/cm2 (protein/diet), among which the Vip3Aa class had the best insecticidal effect. The combination of Cry1Ab and Vip3Aa11 exhibited additive effects at a 5:1 ratio. Cry1F and Vip3Aa11 combinations exhibited additive effects at 1:1, 1:2, and 5:1 ratios. The combination of Cry1F and Vip3Aa19 showed an antagonistic effect when the ratio was 1:1 and an additive effect when the ratio was 1:2, 2:1, 1:5, and 5:1. Additionally, the combinations of Cry1F and Vip3Aa20 showed antagonistic effects at 1:2 and 5:1 ratios and additive effects at 1:1 and 2:1 ratios. In addition to the above combinations, which had additive or antagonistic effects, other combinations exhibited synergistic effects, with variations in synergistic factors (SFs). These results can be applied to the establishment of new pyramided transgenic crops with suitable candidates, providing a basis for FAW control and resistance management strategies.

Mapping malaria vectors and insecticide resistance in a high-endemic district of Haryana, India: implications for vector control strategies.

BACKGROUND: Achieving effective control and elimination of malaria in endemic regions necessitates a comprehensive understanding of local mosquito species responsible for malaria transmission and their susceptibility to insecticides. METHODS: The study was conducted in the highly malaria prone Ujina Primary Health Center of Nuh (Mewat) district of Haryana state of India. Monthly entomological surveys were carried out for adult mosquito collections via indoor resting collections, light trap collections, and pyrethrum spray collections. Larvae were also collected from different breeding sites prevalent in the region. Insecticide resistance bioassay, vector incrimination, blood meal analysis was done with the collected vector mosquitoes. RESULTS: A total of 34,974 adult Anopheles mosquitoes were caught during the survey period, out of which Anopheles subpictus was predominant (54.7%). Among vectors, Anopheles stephensi was predominant (15.5%) followed by Anopheles culicifacies (10.1%). The Human Blood Index (HBI) in the case of An. culicifacies and An. stephensi was 6.66 and 9.09, respectively. Vector incrimination results revealed Plasmodium vivax positivity rate of 1.6% for An. culicifacies. Both the vector species were found resistant to DDT, malathion and deltamethrin. CONCLUSION: The emergence of insecticide resistance in both vector species, compromises the effectiveness of commonly used public health insecticides. Consequently, the implementation of robust insecticide resistance management strategies becomes imperative. To effectively tackle the malaria transmission, a significant shift in vector control strategies is warranted, with careful consideration and adaptation to address specific challenges encountered in malaria elimination efforts.

Characterization of individual spores of two biological insecticides, Bacillus thuringiensis and Lysinibacillus sphaericus, in response to glutaraldehyde using single-cell optical approaches.

Bacillus thuringiensis (Bt) and Lysinibacillus sphaericus (Ls) are the most widely used microbial insecticides. Both encounter unfavorable environmental factors and pesticides in the field. Here, the responses of Bt and Ls spores to glutaraldehyde were characterized using Raman spectroscopy and differential interference contrast imaging at the single-cell level. Bt spores were more sensitive to glutaraldehyde than Ls spores under prolonged exposure: <1.0% of Bt spores were viable after 10 min of 0.5% (v/v) glutaraldehyde treatment, compared to ~ 20% of Ls spores. The Raman spectra of glutaraldehyde-treated Bt and Ls spores were almost identical to those of untreated spores; however, the germination process of individual spores was significantly altered. The time to onset of germination, the period of rapid Ca2+-2,6-pyridinedicarboxylic acid (CaDPA) release, and the period of cortex hydrolysis of treated Bt spores were significantly longer than those of untreated spores, with dodecylamine germination being particularly affected. Similarly, the germination of treated Ls spores was significantly prolonged, although the prolongation was less than that of Bt spores. Although the interiors of Bt and Ls spores were undamaged and CaDPA did not leak, proteins and structures involved in spore germination could be severely damaged, resulting in slower and significantly prolonged germination. This study provides insights into the impact of glutaraldehyde on bacterial spores at the single cell level and the variability in spore response to glutaraldehyde across species and populations.

Fipronil Affects Craniofacial and Heart Development in Zebrafish Embryos (Danio rerio).

Fipronil is a broad-spectrum insecticide that has off-target effects in developing vertebrate embryos. In this study, we investigate treatment of zebrafish embryos with fipronil over the course of 5 days and examine the effects on body length, the cardiovascular system, and craniofacial morphology. We found the insecticide caused shorter body length and a decrease in eye size. By examining specific heart chamber morphology, as well as jaw angle and length, we quantified defects including enlargement of the heart and increases in jaw length and width. Further studies are needed to assess the mechanisms of fipronil's effect on vertebrate development for both environmental and human health concerns.

Construction of coumarin-appended calix[4]arene-based fluorescence sensor for the detection of carbofuran in cabbage.

This study presents a novel approach for the detection of carbofuran (CBF) insecticide by systematically exploring a calix[4]arene-derived fluorescence probe, CouC4S, functionalized with two coumarin-labelled cystamine linkages at the narrow edge of the calix[4]arene platform. The proposed method showed a fluorescence "signal - off" effect when CBF binds with CouC4S by quenching the fluorescence intensity of CouC4S. Its limit of detection was as low as 5.55 µM according to the emission study. The working concentration range for this ligand was observed to be up to 5-65 µM. This method could be applied for the on-spot detection of CBF in real samples such as cabbage by spiking CBFvia in situ experiments, which exhibited a limit of detection of 8.823 ppm. For the further confirmation of CouC4S:CBF binding, cyclic voltammetry, differential pulse voltammetry, powder X-ray diffraction, FT-IR spectroscopy, 1H NMR titration, MALDI-TOF and computational investigations were carried out.

Damage analysis of Pochazia shantungensis (Hemiptera: Ricaniidae) in persimmons.

An invasive species, Pochazia shantungensis (Hemiptera: Ricaniidae), causes serious economic damage to fruit trees. In Korea, this pest is mainly managed using chemical insecticides. However, the management timing and insecticides for P. shantungensis negatively affect honeybee populations. Thus, this study estimated the decision-making level for P. shantungensis in persimmons to decrease insecticide application and increase management efficiency. We determined which developmental stage (i.e., egg, nymph, and adult) affected the damage-related factors (numbers of new shoots and fruit formations, and harvest amount) of persimmons using both spatial analyses and linear relationships. The distribution of P. shantungensis eggs was spatially correlated with the one of persimmon fruit number. However, we did not find any linear relationships between the densities of P. shantungensis eggs and damage-related factors of persimmons. Instead, we found that the density of P. shantungensis correlated with the death of oviposited branches. From the developed model of branch death possibility based on egg mass density, 5.75 egg masses per newly developed branch were proposed as the decision-making level. The findings would help increase the efficiency of P. shantungensis management in persimmon orchards and develop decision-making levels for other insects.

Impact of Three Thiazolidinone Compounds with Piperine Skeletons on Trehalase Activity and Development of Spodoptera frugiperda Larvae.

Trehalases (TREs) are pivotal enzymes involved in insect development and reproduction, making them prime targets for pest control. We investigated the inhibitory effect of three thiazolidinones with piperine skeletons (6a, 7b, and 7e) on TRE activity and assessed their impact on the growth and development of the fall armyworm (FAW), Spodoptera frugiperda. The compounds were injected into FAW larvae, while the control group was treated with 2% DMSO solvent. All three compounds effectively inhibited TRE activity, resulting in a significant extension of the pupal development stage. Moreover, the treated larvae exhibited significantly decreased survival rates and a higher incidence of abnormal phenotypes related to growth and development compared to the control group. These results suggest that these TRE inhibitors affect the molting of larvae by regulating the chitin metabolism pathway, ultimately reducing their survival rates. Consequently, these compounds hold potential as environmentally friendly insecticides.

Multiple toxins and a protease contribute to the aphid-killing ability of Pseudomonas fluorescens PpR24.

Aphids are globally important pests causing damage to a broad range of crops. Due to insecticide resistance, there is an urgent need to develop alternative control strategies. In our previous work, we found Pseudomonas fluorescens PpR24 can orally infect and kill the insecticide-resistant green-peach aphid (Myzus persicae). However, the genetic basis of the insecticidal capability of PpR24 remains unclear. Genome sequencing of PpR24 confirmed the presence of various insecticidal toxins such as Tc (toxin complexes), Rhs (rearrangement hotspot) elements, and other insect-killing proteases. Upon aphids infection with PpR24, RNA-Seq analysis revealed 193 aphid genes were differentially expressed with down-regulation of 16 detoxification genes. In addition, 1325 PpR24 genes (542 were upregulated and 783 downregulated) were subject to differential expression, including genes responsible for secondary metabolite biosynthesis, the iron-restriction response, oxidative stress resistance, and virulence factors. Single and double deletion of candidate virulence genes encoding a secreted protease (AprX) and four toxin components (two TcA-like; one TcB-like; one TcC-like insecticidal toxins) showed that all five genes contribute significantly to aphid killing, particularly AprX. This comprehensive host-pathogen transcriptomic analysis provides novel insight into the molecular basis of bacteria-mediated aphid mortality and the potential of PpR24 as an effective biocontrol agent.

Insights and challenges of insecticide resistance modelling in malaria vectors: a review.

BACKGROUND: Malaria is one of the most devastating tropical diseases, resulting in loss of lives each year, especially in children under the age of 5 years. Malaria burden, related deaths and stall in the progress against malaria transmission is evident, particularly in countries that have moderate or high malaria transmission. Hence, mitigating malaria spread requires information on the distribution of vectors and the drivers of insecticide resistance (IR). However, owing to the impracticality in establishing the critical need for real-world information at every location, modelling provides an informed best guess for such information. Therefore, this review examines the various methodologies used to model spatial, temporal and spatio-temporal patterns of IR within populations of malaria vectors, incorporating pest-biology parameters, adopted ecological principles, and the associated modelling challenges. METHODS: The review focused on the period ending March 2023 without imposing restrictions on the initial year of publication, and included articles sourced from PubMed, Web of Science, and Scopus. It was also limited to publications that deal with modelling of IR distribution across spatial and temporal dimensions and excluded articles solely focusing on insecticide susceptibility tests or articles not published in English. After rigorous selection, 33 articles met the review's elibility criteria and were subjected to full-text screening. RESULTS: Results show the popularity of Bayesian geostatistical approaches, and logistic and static models, with limited adoption of dynamic modelling approaches for spatial and temporal IR modelling. Furthermore, our review identifies the availability of surveillance data and scarcity of comprehensive information on the potential drivers of IR as major impediments to developing holistic models of IR evolution. CONCLUSIONS: The review notes that incorporating pest-biology parameters, and ecological principles into IR models, in tandem with fundamental ecological concepts, potentially offers crucial insights into the evolution of IR. The results extend our knowledge of IR models that provide potentially accurate results, which can be translated into policy recommendations to combat the challenge of IR in malaria control.

Microsclerotia from Metarhizium robertsii: Production, ultrastructural analysis, robustness, and insecticidal activity.

Microsclerotia (MS) are considered one of the most promising propagules for use as active ingredients in biopesticides due to their tolerance to abiotic factors and ability to produce infective conidia for the control of pests. Therefore, the objective of this research was to establish the conditions required to induce the formation of microsclerotia in Metarhizium robertsii Mt004 and to study its development process, tolerance to abiotic factors and insecticidal activity of MS-derived conidia. M. robertsii started to form hyphal aggregates after 2 days and looked more compact after 8 days. MS were mature and pigmented after 20 days. The final yield was 2.0 × 103 MS/mL and MS size varied between 356.9 and 1348.4 µm. Ultrastructure analysis revealed that mature MS contained only a few live cells embedded in an extracellular matrix. Mature MS were more tolerance to UV-B radiation, heat and storage trials than conidia from Solid State Fermentation. MS-derived conidia were as virulent as conidia against Diatraea saccharalis larvae. These results showed that MS are promising propagules for the development of more persistent and efficient biopesticides for harsh environmental conditions. Our findings provide a baseline for production and a better understanding of microsclerotia development in M. robertsii strains.

Biochemistry and transcriptomic analyses of Phthorimaea absoluta (Lepidoptera: Gelechiidae) response to insecticides.

Phthorimaea absoluta is an invasive solanaceous plant pest with highly devastating effects on tomato plant. Heavy reliance on insecticide use to tackle the pest has been linked to insecticide resistance selection in P. absoluta populations. To underline insights on P. absoluta insecticide resistance mechanisms to diamides and avermectins, we evaluated the transcriptomic profile of parental (field-collected) and F8 (lab-reared) populations. Furthermore, to screen for the presence of organophosphate and pyrethroid resistance, we assessed the gene expression levels of acetylcholinesterase (ace1) and para-type voltage-gated sodium channel (VGSG) genes in the F1 to F8 lab-reared progeny of diamide and avermectin exposed P. absoluta field-collected populations. The VGSG gene showed up-regulation in 12.5% and down-regulation in 87.5% of the screened populations, while ace1 gene showed up-regulation in 37.5% and down-regulation in 62.5% of the screened populations. Gene ontology of the differentially expressed genes from both parental and eighth generations of diamide-sprayed P. absoluta populations revealed three genes involved in the metabolic detoxification of diamides in P. absoluta. Therefore, our study showed that the detoxification enzymes found could be responsible for P. absoluta diamide-based resistance, while behavioural resistance, which is stimulus-dependent, could be attributed to P. absoluta avermectin resistance.